Multipolar dance could flip Earth’s magnetic field

Researchers in France have developed a new model of Earth’s magnetic field that includes a simple explanation for why it has flipped direction many times throughout Earth history.

Most geophysicists agree that the main component of Earth’s magnetic field is generated by convection currents in the molten iron of the planet’s core. This dipole field — which defines the Earth’s magnetic poles — has reversed polarity tens of thousand of times in the past. We know this because ancient field configurations are “frozen” into the rocks, as magnetic particles align with field lines.

Various theories have been put forward to explain the reversal mechanism but they are usually highly complex, where random variations in the flow of the liquid core are the main triggers.

A meeting of magnets

Now, François Pétrélis and his colleagues of the École Normale Supérieure and Institut de Physique du Globe have simplified the problem by reducing the Earth’s field to a set of basic equations, which show strong agreement with the predictions of more complicated models. They did this by focussing on the interplay between the dipole and and quadrupole components of the field.

“We are proposing that reversals result from the competition between the dipolar mode and a second, unstable, dynamo mode,” said Petrelis.

A geomagnetic field reversal takes approximately 10, 000 years — a very short period on a geological timescale — during which time, the field drops to approximately 10 percent of its normal intensity. In previous models, fluctuations in the flow of molten iron “switch off” the main dipole component and then regenerate it with the opposite polarity.

A deep-Earth salsa dance

In this new proposal, it is not the turbulent flow but a second field known as a “quadrupole” that drives the reversal. Leading up to the flipping of the poles, the dipole reduces in intensity as the quadrupole grows in strength. Once the dipole component has vanished it can start to grow again, as the quadrupole now drops in strength.

“This is a study — like a number of others — in the spirit of replacing a very complicated physical system by a highly simplified low-dimensional set of equations,” said Ulrich Christensen, a geophysicist at the Max Plank Institute for solar System Research in Germany.

Petrelis told physicsworld.com that direct measurements of the Earth’s magnetic field suggest that we are not due a reversal any time soon.

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THE SUN MAY FLIP EARTH'S MAGNETIC FIELD

Although the Sun's visible photosphere provides the illusion of a solar "surface" that separates the Earth from the Sun, the Earth is actually moving through the outer layer of the Sun - the heliosphere.

The Earth is gravitationally, electrically and magnetically connected to the Sun. Solar cycles are cycles of deep-seated magnetic fields that periodically poke through the solar "surface" as sunspots, solar storms, and violent solar eruptions.

Thus Earth's magnetic field may be flipped by the same deep-seated magnetic fields that produce cycles of solar magnetic storms: The energetic neutron star at the core of the Sun, about 1 AU from the core of the Earth.

Atmosphere may drive magnetic direction

The question would still remain about what drives the quadrapole.

I would suggest that the mechanism behind the magnetic polarity has to do with the direction of the atmosphere. The upper atmosphere is highly charged and the winds running around the Earth turn this into a weak current. This weak current generates a small magnetic field which is then magnified by the Earth's core. Some studies have suggested that magnetic reversals are accompanied by major climatic change such as the onset of ice ages and reversals in the prevaling winds. Changes in climate may in turn be driven by changes in the environment by the sun. This would provide a simple causal mechanisim for the the reveral of the poles.

Sun contains a neutron star?

Dear reader,

Re: Prof Manuel's discussion, I am very proud to see this example of science being a broad, inclusive church.

I feel that Oliver Manuel is being somewhat disingenuous, though:- There is no "of course" about a neutron star within the sun. It is his own theory, and it is good to see him challenging orthodoxy in this way, but it is certainly not accepted by the broader scientific community.- Flavor-changing has been "clearly observed" in neutrinos from reactors and the sun, at the KamLAND and SNO experiments (e.g. A.B.McDonald, Nucl.Phys. A751, 53-66, 2005 and arXiv:nucl-ex/0412005) so it's not accurate to describe it as a "fudge factor".

Effects of Reduced Terrestrial Magnetic Field

"during which time, the field drops to approximately 10 percent of its normal intensity"

One would think that this would be of concern to the scientific community. Wouldn't that drastic of a drop in magnetic field strength cause a commensurate 90% increase in the influx of cosmic rays and charged solar particles?

MYSTERIOUS SCIENCE AND BLACK MAGIC

D. Swift is right.

The idea of a neutron star at the core of the Sun is certainly not accepted by the broader scientific community.

Of course, they also have no explanation how d- and l- amino acids were separated before life started, why solar cycles follow changes in solar inertial motion, why supposedly dead nuclear matter explodes to produce the most violent cosmic events, why Hydrogen (the supposed stellar fuel) is continuously being emitted (as an exhaust gas) from the Sun and other stars, etc., ad infinitum

Of course, they also have no explanation how d- and l- amino acids were separated before life started, why solar cycles follow changes in solar inertial motion, why supposedly dead nuclear matter explodes to produce the most violent cosmic events, why Hydrogen (the supposed stellar fuel) is continuously being emitted (as an exhaust gas) from the Sun and other stars, etc., ad infinitum

d- and l- amino acids were likely separated due to parity violation which is a factor in their creation and structure. This does mean circularly polarized light from synchrotron emission of neutron stars could cause this, but it doesn't mean there is a neutron star at the core of our sun.

Complex spectral signatures of compounds have been found within the interstellar medium and our galaxy is old. So the origin of amino acids doesn't have to be our Sun.

Also Hydrogen is only emitted at the rate of about 3x10^-14 kg/year. This would require more than 10^13 years before the entire mass of the Sun would be dissipated at current ejection rates and the sun is only ~4.57x10^9 years old.

I suggest you read An Introduction to Modern Stellar Astrophysics by Ostlie and Carroll